The successful use of fluorescent brightners on sheets has up to this time relied on the addition of cationic groups to fluorescent molecules, or the utilization of alum sensitive molecules, starch-based fluorescent molecules or polymer-bound fluorescent molecules. (Mehlretter, C.L., I.&E.C. Prod. Res. 8:77-79 (1969); GB Patent No. 1,142,504; DE Patent No. 1,696,165). However, no prior product conveyed to the substrate high fluorescence characteristics as well as excellent retention of the high brightness characteristics, i.e., the fluorescent brightener itself.
U.S. Pat. No. 3,912,697 to Eastman Kodak Co. discloses light sensitive polymers and their use in photographic reproduction. The polymers which form the backbone of the light sensitive polymers include hydroxyl-containing polymers such as cellulose and its partially esterified or etherified derivatives or anthranilic acid polymers such as polyvinyl anthranilate. However, no covalently bound anthranilic acid-cellulose derivatives are mentioned therein.
U.S. Pat. No. 4,273,873 to UNITKA LTD. of Japan discloses and claims a process for preparing an antithrombogenic polymeric material by reacting various compounds including antithrombogenic products, polymeric material such as cellulose or cellulose accetate and an anthranilic acid derivative to cause the various reactants to covalently or ionically bind to the polymeric material. However, the prior art patent does not disclose a product where anthranilic acid or a derivative thereof is covalently bound to a cellulose-type polymer. Moreover, the prior art polymer contains a synthetic fibrinolytic compound pound and a fibrinolytic enzyme, and is intended as antithrombogenic materials. The specific anthranilic acid derivatives suitable for use in the prior art invention are described in columns 3 and 6 of the patent.
U.S. Pat. No. 3,821,282 describes polymerizable anthranilic acid esters obtained by heating acrylic or methacrylic acid esters with isatoic anhydride. The resulting polymers are polymerizable esters. This patent does not mention utility as fluorescent brightening agents.
U.S. Pat. No. 4,501,767 discloses a method for forming multi-coats and discloses reaction products of acrylic compounds and aminobenzoic acids in the preparation of an accelerator. There is mentioned the reaction product or ortho-, meta- or para-aminobenzoic acid with a polymerizable unsaturated carboxylic acid or a polymerizable unsaturated alcohol. No products resulting from this reaction are described as such in the patent. Moreover, there is no suggestion of utility of the reaction product as a fluorescent brighten,er.
U.S. Pat. No. 3,933,675 to Willett discloses improved curing agents having long pot life for use with urethane elastomers. These agents are prepared by reacting in an acid medium orthochloroaniline, an ester of anthranilic acid and formaldehyde in selected molar ratios.
Re 28,541 discloses diamine cured polyurethane compositions with unusually long pot life which cure rapidly at elevated temperatures. The compositions are prepared by combining a prepolymer of di- or poly-isocyanate and hydroxy-terminated polyether or polyester of molecular weights 150-3,000 daltons.
U.S. Pat. No. 3,943,150 to Kashkina et al discloses a salt of beta-diethyl aminoethyl ester of p-aminobenzoic acid with the acetal of polyvinyl alcohol and glyoxylic acid. The patent also provides a method of preparing the compound comprising reacting the acetal of polyvinyl alcohol and glyoxylic acid with beta-diethylaminoacetyl ester of p-aminobenzoic acid in an aqueous medium and isolating the desired product from the resulting solution.
Accordingly, there is still a need for improving the brightness characteristics of cellulosic products while at the same time improving their brightness retention and preserving their low toxicity.